Japan’s coast guard has held a joint exercise with counterparts from the United States and the Philippines, as the three Pacific nations beef up defense cooperation in the face of China’s expanding maritime activities.

Helicopters buzzed in the shadow of a smoldering volcano and boats rescued dummies from the sea last week in a show of maritime unity by Japan, the United States and the Philippines.

Japan, the United States, and the Philippines carried out a major coast guard drills together on Friday. The drill took place in the waters off Kagoshima, a southern part of Japan. This event comes at a time when worries are growing about China’s increasing actions in the Pacific Ocean.